During the three-year period September 1, 1990 through August 31, 1993 we will continue to operate our multiwire area diffractometer facility, and to optimize its functioning for maximum production of high quality data. This optimization will be achieved through software enhancements to make the system more accurate, more flexible, more interactive, and easier to use. We will develop the capability to process data off-line to ensure optimum use of data from rare crystals. We will also develop the capability to scale data, make Wilson plots, calculate Bijvoet mate differences, and compute difference Patterson and difference Fourier maps, all concurrently with data measurement. We will continue developing an MCP delay line x-ray detector by constructing and testing a full size version of the 40 mm prototype developed during the present period. This detector, when perfected, will result in a significant advance in the state of the art of x-ray detectors. It will permit measurement of data on much larger unit cells than is now possible, will speed up data collection, and will permit more accurate measurement of Bijvoet pairs than is now possible.